Generally, fleshtone correction circuitry for selectively modifying the hue of a color television receiver is expected and provided in modern-day television receivers. As a matter of fact, fleshtone correction circuitry which is automatic rather than manually operated is the generally accepted standard.
More specifically, fleshtone or hue compensating apparatus utilizing both active and passive components has been employed in color television receivers. In either case the chrominance or reference oscillator signals applied to demouulator stages are altered in phase to automatically reduce variations of color signals along the fleshtone and cyan axes of a standard chrominance diagram and effect enhancement of fleshtone reproduction by the receiver.
However, it has been found that such fleshtone enhancement is frequently and unfortunately accompanied by undesirable alteration of colors in other areas of the standard chrominance diagram. For example, colors which should appear green, such as grass, often undesirably appear blue or yellow when fleshtone enhancement is employed.
One known attempt to alleviate the above-mentioned undesired alteration of colors, other than fleshtones, by hue compensation circuitry is disclosed in the cross-referenced application entitled "Gated Automatic Tint Control Circuit". Therein, phase alterations of the color reference signals to effect fleshtone enhancement are utilized only during a specific gated portion of the chrominance diagram. Specifically, the gated period or altered phase angles occur only for colors in the first and second quadrants of the standard chrominance diagram. Thus, fleshtones are enhanced by altering phase angles but colors in the other quadrants, such as green and blue for example, are unaffected by the enhancement circuitry.
More specifically, it has been found that an activated fleshtone correction system, such as a system gated or turned on by a positive R-Y signal in the first and second quadrants of the standard chrominance vector diagram for example, tends to require readjustment of the tint controls. In other words, activation of the fleshtone correction circuitry alters the fleshtone reception whereupon manual tint control adjustment is required. However, altering the tint control also alters all colors including fleshtones whereupon the colors excluded from the gated fleshtone correction system, blue and green for example, are undesirably altered. Thus, green grass will tend to appear yellow or blue skies will tend to be green.
Although the above-mentioned "Gated Automatic Tint Control Circuit" has provided numerous advantages and enhanced reception in color television receivers, it has been found that there are areas which still leave something to be desired. Also, a reduction in cost and complexity of the circuitry is obviously desirable. Moreover, an improved response without adverse effect on cost is also an obviously desirable condition.